One approach to improve reconstitution of immunity against viruses following allogeneic HSCT is to adoptively transfer donor-derived virus-specific T lymphocytes, which has been well documented with proven success. Existing evidence suggests that adoptive cellular therapy (ACT) can be an effective approach for treating viral reactivation following allo HSCT, with a minimal risk of inducing GVHD. The major advantage to the patient is likely to be avoidance of extended periods of therapy with antiviral medications that have significant associated morbidities, and sometimes require inpatient care. From a pharmacoeconomic viewpoint this would translate into a reduction of costs associated with standard antiviral therapies compared to the cost of adoptive cellular therapy.